Abstract: The physiological activity of diBcAMP by various classical bioassay methods of cytokinin was studied. It exhibits the cytokinin-like activity in many ways of biological response, such as: the unfolding of etiolated barley leaf, the expansion of radish cotyledon, the expansion and greening of cucumber cotyledon and the inhibition of the elongation of mung-bean hypocotyl, etc. The activity of 1 mM diBcAMP was approximately the same as the activity of 0.044 mM benzyladenine in the most of the tests. However, the activity of 1 mM diBcAMP was found to be higher than the optimal concentration (0.044 mM) of benzyledenine in the radish cotyledon under the expansion test. There was no toxicity of diBcAMP in all of the bioassay methods used, even with higher concentration.